So here's the rundown. After you guys kindly helped me fix the issues with my circuit I've built a few customised sonic screwdriver props for prople using these electronics (so far, no issues). The most recent one however has me a bit stumped. Circuit is constructed according to this drawing provided to me previously, only difference is an additional LED wired in parallel, all powered by 5x LR41 batteries.
So I put this screwdriver together, all seemed to be working well and so I sent it off to the customer. A few hours after recieving it and telling me how happy he is with it, he says he's having issues with the light and sound (I have video showing the exact issue that I can't upload directly so if anyone can let me know how best to send it here that'd be great)
Basically it seems to work as intended (button is pressed, lights and sound play) but after holding the button down for a short time, the lights rapidly dim and eventually both light and sound stop functioning. At first I'd thought it was an issue that caused the batteries to drain, but when it arrived back with me earlier this morning for repairs it seemed to have "re-charged" itself and appeared perfectly normal. I tested it and discovered that holding the button down for 50 seconds straight causes the light and sound to die, and it goes back to normal after about 10 minutes but then the lights only last about 20 seconds before dying.
Basically, I'm a bit stumped! I know it's not an issue with the batteries holding charge as they still work, but I honestly don't know enough about this stuff to theorise on what the actual issue could be.
Sorry that went on a bit.. just trying to get all the relevant info in there! Let me know if I've missed anything important that could help figure this one out.
Examine the bad screwdriver carefully to be sure all your wiring and components values are correct.
Build an identical circuit, or grab one, and see if the two instances perform identically. Basically look for something that might inadvertently be different in the bad unit.
Do a few experiments. If all you did is add the LED and resistor, it makes no sense to look at software for what feels like a power supply issue.
Do you have a voltmeter of any kind?
I'd be curious to see the voltage the batteries are delivering over the time that it takes to go from happy to unhappy, 50 seconds.
Can you try the circuit with same voltage as a fresh stack of LR41 cells coming instead from a power supply, or even just very larger batteries?
And also, try temporarily removing the LED, which if I understand would again be identical to several instances that operate well.
OK, I haven't found the maximum recommended discharge rate for any kind of LR41, who knew there were different types of the same cell?
Anyway, I've been picking up discarded vaping devices around the beach, just to get them out of any harms way.
I take them apart and find a 3.7 volt nominal Lipo cell powering them.
I'm still thinking you have a power supply issue, experiments will tell us. A Lipo cell would be a better choice for this relatively heavy current draw.
You could probably find one that meets you physical constraints.
All the wiring is intact so there shouldn't be an issue there. I recently moved and my multimeter got lost in the chaos but a new one should arrive in a few days so after that I'll be able to measure the voltages.
It's currently being powered by 5X LR41 batteries, I've also got some more of those on order so when they arrive I'll be able to replace the ones in there currently with fresh ones, and build an identical circuit.
Thanks for the quick responses! I'll post again in a couple of days when my supplies have arrived.
If it isn't cooked already.
There is a good reason manufacturers publish data sheets with "Maximum Voltage" quoted.
Most quote that as being 5.5v so up to you.............
My customer is concerned about lowering the power as that'll lower the volume, is there any way to increase the volume while lowering the power to a safe level? or do I just need to find batteries with the same voltage output/dimensions but a higher operating voltage?
Is there a simpler way to fix the issue instead of completely re-wiring the whole thing? space for wires inside the screwdriver is extremely limited so I'm not too keen to be changing the circuit around too much.
Obviously need to do more research but I'm thinking that just removing a battery may be the best course of action. My customer probably won't be thrilled about the lower volume/LED brightness but it is what it is!
The only issue removing one or two cells from your battery will solve is that you will be less likely to destroy your microprocessor chip.
As @anon85221860 has stated, you are probably getting away with it since the battery voltage sags enough under the load you place upon it, far more current than an LR14 is usually expected to deliver.
So you screwsdriver will continue to eat through the battery in short order. I am surprised it recovers from the mistreatment and lives to give another short performance.
Until you can measure and observe and experiment along the lines suggested here we are left to speculate and base our opinions on experience rather than evidence.
You haven't said what LR14 cell you are using. I may have misread, but in my researches earlier I thought I saw the same number attached to some cells of various chemistries, so if you have a link to the exact cells that would be helpful.
Normal use of an LR14 it wouldn't matter if you had one kind or another. In this deployment, one may work better than another.
a7
Just face facts...the voltage applied to the uC is way too high.
It is essentially a crap design.
Need will be apply correct voltage to the uC and deal with volume of output in a better way, perhaps an extra amp.
There are small modules available cheap as chips.
